Sheath Voltage Limiters
Sheath Voltage Limiters (SVL) are an economic solution for safeguarding expensive cable installations.
Description
Selection Guide
Downloads
Description
They are highly reliable and effective at managing cable sheath voltage rises and the associated power flows that can result under fault conditions.
Insulect manufacture an extensive range of quality 20kA zinc oxide sheath voltage limiters (SVL’s). Voltages: 1.5kV to 9.0kV
Selection Guide
Generally the following must be considered:
- SVL Rated voltage must be equal to or greater than the induced sheath voltage caused by the maximum system fault current (i.e. The SVL should not conduct during normal fault conditions).
- From the cable manufacturer, obtain cable data to determine the maximum voltage withstand for an 8/20 and 4/10 microsecond lightning or switching induced voltage.
- From the SVL data characteristics table, check that the SVL selected has residual voltages less than the rating of the sheath (i.e. the SVL’s main function is to protect the sheath under these conditions).
65V is generally the maximum allowable voltage due to normal load currents. Short circuit and switching currents will cause much higher voltages (several kV).
These induced voltages must be calculated by the client’s engineers before an SVL can be selected.
Note that all bonding cables used for earthing the sheath must also be able to withstand these voltages.
Downloads
Technical Specifications
SVL Type
-
TZS1.5
TZS3.0
TZS4.5
TZS6.0
TZS7.5
TZS9.0
Rated Voltage
kVrms
1.5
3.0
4.5
6.0
7.5
9.0
Maximum Continuous Operating Voltage
kVrms
1.3
2.5
3.8
5.1
6.4
7.7
Rated 8/20µs current
kA
20
20
20
20
20
20
20kA 8/20 20 shot duty cycle with power frequency voltage applied 1s/shot
kVrms
1.8
3.6
5.4
7.2
9.0
10.8
High current 4/10µs withstand
kA
100
100
100
100
100
100
Low current rectangular 2000µs duration withstand (20) shot
A
1000
1000
1000
1000
1000
1000
Energy absorption (on each of 20 shots)
kJ
5
10
15
20
25
30
Energy absorption on 2 shots before cooling
kJ
6.5
13
20
26
33
40
Maximum 8/20µs residual voltage at:
-
-
-
-
-
-
-
1.5kA
kV
3.6
7.1
10.5
14.1
17.6
21.1
3kA
kV
3.7
7.4
11.0
14.7
18.4
22.1
5kA
kV
3.9
7.7
11.5
15.4
19.2
23.0
10kA
kV
4.1
8.2
11.8
16.3
20.4
24.5
20kA
kV
4.4
8.8
13.2
17.6
22.0
26.4
40kA
kV
4.9
9.7
14.5
19.3
24.2
29.0
100kA (4/10µs)
kV
6.0
12.0
18.0
24.0
30.0
36.0
Residual at 15kA 1µs current rise time
kV
4.7
9.3
14.0
18.6
23.3
28.0
Resistance at 2500Vdc
Ω
N/A
N/A
> 107
> 107
> 108
> 108
Resistance at 1500Vdc
Ω
> 107
> 107
> 107
> 107
> 108
> 108
Temporary over-voltage (TOV) 1s withstand: from no prior load after 7kJ/kVrms of rated voltage
kV rms kV rms
1.9, 1.8
3.9, 3.7
5.9, 5.6
7.8, 7.4
9.8, 9.3
11.8, 11.2
TOV of 5kV dc withstand time
s
∞
2
∞
∞
∞
∞
TOV of 3.5kV dc withstand time
s
∞
50
∞
∞
∞
∞
TOV of 2.5kV dc withstand time
s
2
∞
∞
∞
∞
∞
Current at 5kV dc
A
∞
3
10-4
10-5
10-5
10-5
Reference Current
mA dc
1
1
1
1
1
1
Reference Voltage (minimum)
kV dc
2.1
4.18
6.28
8.36
10.46
12.54
Mechanical robustness
-
Dropped 1.5m without internal damage
